Handheld optical aids such as binoculars are important tools which are commonly used by astronomers, hunters, bird watchers, military personnel, spectators at sporting events and dramatic or musical productions, and many other people--both amateurs and professionals. Such optical aids greatly enhance the user's optical perception by providing magnified and brighter images of the subject under study.
A significant problem in the use of such aids is the difficulty of holding them still enough, aggravated by fatigue to the user's arms and hands in protracted usage. Inability to hold optical aids steady over a period of time causes a dancing, jiggling image which largely negates the advantages offered by the improved optical image.
The problem of holding binoculars still enough for effective usage has long been recognized by astronomers. The most common method of overcoming this problem is to mount the binoculars to a common photographic tripod. While this approach solves the problem of unsteadiness, the tripod itself usually interferes with the position that the body of the user must assume when viewing objects at a angle of altitude from the horizon. Furthermore, few tripods are sufficiently tall to position binoculars high enough for a tall user, when the user is looking up from a standing position.
Accordingly the literature reveals various efforts to construct tripod attachments that mitigate the drawbacks of standard tripods. One such design, due to Steve Kufeld of Huntington Beach, Calif., is noted in the August 1979 issue of Sky and Telescope magazine, at pages 110 and 112.
Kufeld's device, a counterbalanced mounting atop a heavy-duty tripod, is illustrated in use by a photograph of a person sitting on a stool and looking through a pair of binoculars fixed to the mounting. Through this apparatus is apparently of considerable utility, the photograph itself shows a principal disadvantage of such devices, as the user leans forward awkwardly from the stool to bring his eyes to the appropriate distance from the fixed tripod. Presumably the stool could be moved to a better position for at least some viewing angles; however, the picture also suggests another drawback--namely, that movement of the stool (or of the user's position if standing) is required to change the vertical viewing angle.
Another tripod design aimed at overcoming this latter drawback is described by Rudolf Mandler of Deubach, West Germany, in the July 1982 issue of Sky and Telescope at pages 89 and 90. Mandler's tripod mount has an "inverted yoke" that carries the binoculars in such a way that "the binoculars swing in a vertical plane around a pivot at [the] neck." By virtue of this action, it is "possible to view objects all the way to the zenith without twisting [the] body." This swinging action is a very important feature of Mandler's tripod and will be discussed further below.
A less common but frequently publicized approach has been to build special chairs or chair attachments that support the binoculars through mechanical arms and brackets. Such arrangements provide more comfortable viewing positions for the user's body, particularly at higher viewing angles.
Chris Baetens, of Boechout, Belgium, offers one of the simplest of such devices, shown in the February 1985 issue of Sky and Telescope at page 171. His device is made from an old revolving desk chair fitted with an adjustable framework to support the user's back, as the user assumes a near-reclining position to view the stars. Casters under the entire assemblage permit the user to swivel the chair, and adjustable arms support the binoculars above the back portion.
Once the binocular support arms and the back framework are properly adjusted for the particular user's comfort and for the desired altitude angle, such a device supports the binoculars steadily, relieving the user's hands of this task. It of course offers considerable viewing satisfaction for the amount of design and construction effort invested. To change viewing angles, however, the user apparently must get up, adjust the back framework and probably the support arms as well, and then get back into the apparatus under the support arms.
John Talbot, of Camarillo, Calif., writing in the same publication at page 172, has described a system that avoids this necessity. His chair rocks for altitude variation and rotates in azimuth, permitting a good view of the sky from about twenty-five degrees of altitude to the zenith--with one stop for chair adjustment along the way.
Pearson Menoher, of Greenwich, Conn., in the January 1974 issue of Sky and Telescope at pages 51 through 55, discloses a more elaborate apparatus that eliminates the need for getting up and sitting back down to make adjustments. His apparatus is a motorized observing chair which tilts about a vertical axis for altitude-angle variation, and which rides a wheel-and-track suspension for azimuth variation. The azimuth system is driven by a third-horsepower electric motor. This system may represent the ultimate in investment for binocular-viewing comfort, though perhaps not the ultimate in design elegance.
Emphasizing the latter, or at least aiming to make the most of a much more modest investment in time and materials, are observing-chair designs introduced by John Riggs, of Kenmore, N.Y., and by Burt Leifer of Fort Wayne, Ind. These appear in Sky and Telescope for, respectively, February 1981 (pages 162 through 164) and May 1979 (pages 487 and 488).
Each of these two approaches provides a chair with a simple azimuthal pivot about a vertical axis, and more importantly (as will be seen) a vertical swinging action for the binoculars themselves about a horizontal axis that is generally adjacent to the user's neck.
Most of the tripods and chair brackets discussed above are difficult to adjust when changing viewing angles. These devices frequently require several separate adjustments to obtain the right position in both height and angle. The Mandler tripod and the Riggs and Leifer chairs minimize these problems by the swinging action of the binoculars about axes adjacent to the viewer's neck.
To understand this advantage, it is necessary to refer to the physiology of a typical viewer in scanning vertically over large angles of altitude. Generally, viewing seems to be most comfortable when the eyes are directed roughly "straight ahead" in relation to the head. There is a slight range of eye travel within which a person can comfortably view objects above or below a normal straight line of sight, relative to the person's head, but the principal way of shifting the direction of one's gaze by large angles is to move the head itself. For comfortable protracted viewing, therefore, it is necessary to allow for shifting of the head: translational and rotational movements naturally accompany rotation of a person's direction of view.
The multiple-adjustment problem mentioned above, as recognized by Mandler, Riggs, Leifer and others, arises from these translational and rotational movements. These natural movements of a person's head cause the eye position to traverse an arc when the head moves between a horizontal and an elevated viewing position. For present purposes this arc may be regarded as very roughly circular, with an apparent or effective center of motion that is near the person's neck.
Thus both Mandler's tripod-attachment "yoke" and the binocular-supporting "fork" of Riggs' and Leifer's chairs pivot about axes adjacent the user's neck. The location of the pivot axis relative to the user's body is discussed explicitly by both Riggs and Leifer. In each case the binocular eyepiece, being fixed to the yoke or fork, revolves about the same respective axis. As shown in Mandler's illustrations, however, the line of sight itself--that is, the centerline of the ocular--preferably does not pass through that mechanical-rotation axis.
There remain several problems, however, with the inverted "yoke" or "fork" designs of Mandler, Riggs and Leifer.
First, the viewer must remain in a fixed position with respect to the mechanical-rotation axis of the yoke or fork. In other words, the viewer must stand in essentially the same spot continuously to use Mandler's tripod; or he must sit in essentially the same spot in Riggs' or Leifer's chair. He must be in the same position relative to the rotation axis, or his line of vision will not comfortably align with the centerlines of the oculars. After a time these requirements lead to a certain amount of discomfort. In effect the viewer becomes saddle-sore.
Second, in the design of these three swinging-mount systems the translational and rotational movements of the user's head are not only accommodated (which is desirable), but are actually required to supply all of the vertical variation in angle of view. This requirement is not desirable, because it means that to view parts of the sky near the zenith either the entire chair must tilt (as in Menoher's elaborate device) or the user's head must be tilted far back relative to his torso. The uncomfortable neck angle that results is quite plainly depicted in the photograph at page 163 of the Riggs presentation in Sky and Telescope, and is piquantly confirmed by the author's comments about the importance of his headrest.
Third, in each of the Riggs and Leifer chairs, the positioning of the binocular-mount rotation axis relative to the body of the chair must be tailored to the personal dimensions of the individual who will use the chair. Thus Riggs says:
I eventually found the axis position ideal for my eye. Careful measurements were then transferred to the layout of the inverted fork that carries the telescope, and to the layout of the large triangular seat box. PA1 Leslie Peltier has pointed out that the axis of movement of his head up and down is in line with his ears. Glenn found that his axis was 13/4" below the ear opening. Each observer will have to determine this point before beginning construction.
Leifer refers to earlier comment thus:
Fourth, the swinging-arm mounts in the Mandler, Riggs and Leifer devices all require the positioning of the swinging structure at the sides of the user's head. As the user tilts his head up and down, he always hand-adjusts the swinging structure up and down too; thus it remains at the sides of his head. This swinging structure of course also has a crossbar, carrying the binoculars. The crossbar passes all the way across his field of peripheral vision--not only across the user's face as such, but across the entire distance between the swinging-structure elements at both sides. The user moves this crossbar too so that it tracks his head movements and is always across both sides of his peripheral field of view.
Although of course the device is used generally in darkness, nonetheless there will remain for many users a continuing sensation of being enclosed or even confined. The crossbar and the swinging-structure side elements together form a moving cage, always occupying both sides of the user's peripheral vision. In other words, these tend toward the claustrophobic. This tendency is badly aggravated by the requirement that while viewing the user keep his body in practically the same position relative to the tripod or chair.
Fifth and finally, all of the tripod and chair-bracket systems--even those of Mandler, Riggs and Leifer--are limiting in that their size and in some cases their weight inhibit the user's freedom of movement.